The Function of Vitamin D
As nutritionists, we know how important a role vitamin D plays in maintaining calcium homeostasis in our body, which is key to
bone health. It improves calcium absorption in the intestines, reduces calcium losses
through urine and mobilizes calcium from the bones when needed.
Vitamin D Deficiency
Vitamin D deficiency is becoming an increasingly common problem, often as a result of wearing clothing that covers most
of the body, using sunscreen, deliberately avoiding sunlight or living in
areas at high latitudes. A lack of this vitamin can lead to serious
health problems such as osteomalacia/osteoporosis. It is also linked to high
blood pressure, type 1 diabetes, multiple sclerosis and even some types of cancer.
Supplementation with vitamin D can be beneficial, but it is important to consult a doctor in order to
avoid adverse effects such as vitamin D intoxication.
Getting Vitamin D Naturally
We often hear that we should go out in the sun in order to get vitamin D. This is partly true.
We do not absorb vitamin D directly from sunlight; rather, the sun’s rays help the inactive form of
vitamin D in our skin convert into the active form at a temperature of 37°C. Under ideal
conditions, 80-90% of vitamin D comes precisely from this process.
A simple 20-minute walk, during which the whole body is exposed to the sun’s rays, can
lead to the creation of 250 µg of vitamin D3 in the skin. This is enough to meet the daily needs for
vitamin D (>30 ng/mL 25-OH D). Vitamin D3 is also found in foods of animal origin
such as egg yolks, oily fish, fish oil and dairy products.
Vitamin D Intake Through Food
Vitamin D intake through food depends on the geographical area, tradition and culture. In Japan,
the biggest source of vitamin D is fish and fish oil, while in some European countries, such as the Czech Republic,
it comes from eggs. The main sources of vitamin D are meat, fish and eggs. It is especially beneficial to consume wild
fish such as mackerel, salmon, herring, cod and tuna, while freshwater fish such as trout contain a somewhat
smaller amount of vitamin D. Seafood such as mussels, shrimp and oysters have negligible
amounts of vitamin D compared to fish.
Eggs are also a good source of vitamin D, especially the yolks, regardless of the type of poultry (chicken,
duck, goose or quail). Chicken meat and liver contain less vitamin D, while among livestock the
richest source is pork, but this depends on the cut of meat, the pig’s diet and how much time it
spent in the sun.
Milk and dairy products are an important source of vitamin D, especially for children and infants. On the market there are
milks and baby formulas with added vitamin D. Dairy products rich in
vitamin D include butter, full-fat cheeses and sour cream.
The Stability of Vitamin D
Vitamin D has relatively high stability at high temperatures and during food processing such
as baking, frying and cooking, whether it comes from natural sources or is an additive in products.
It is also stable during the long-term ripening of cheese and the storage of dairy products with a long shelf
life.
For the health of the bones and the whole body, it is important to ensure an adequate intake of vitamin D through
sun exposure and a proper diet. Always consult an expert before taking
supplements in order to ensure optimal results without the risk of overdose.
Jovana Arsović
professional nutritionist-dietitian